Modern day electronic equipment often requires galvanic isolation between the high voltage side and control signal side thereof. Galvanic isolation means that no electrical current can flow directly between the high voltage side and the control signal side, as there is no direct electrical contact. However, even though the high voltage side and control signal side are galvanically isolated from one another, a signal can flow between the two.
One piece of electronic equipment, among many, that might require the aforementioned galvanic isolation is an x-ray machine. Typically, very high voltages are required to operate an x-ray machine. However, these very high voltages need to be shielded from the patient and/or operator of the x-ray machine. Another piece of electronic equipment that might require the aforementioned galvanic isolation is a motor controller. For example, galvanic isolation could be used to electrically separate the 220 Volt motor windings from the control module.
In each of the uses of galvanic isolation, the solution needs to be fast, compact, capable of integration into the preexisting systems, and immune to electromagnetic noise. Moreover, many of the solutions must receive certification from the Association for Electrical, Electronic & Information Technologies (VDE), Underwriters Laboratories (UL), CSA International (CSA), International Organization for Standardization (ISO), etc. These certifications often require robust solutions (e.g., reliable for an extended period of time) capable of withstanding extremely high DC voltages, as well as RMS voltages. These certifications also require for the solutions to have a relatively high transient immunity (e.g., the ability to handle voltage spikes).
Given the aforementioned desires for galvanic isolation, as well as the requirements thereof, the electronics industry has focused on a number of different solutions. One such solution is the placement of a discrete high voltage capacitor (or pairs of capacitors) between the high voltage side and control signal side of the electronics equipment. These discrete high voltage capacitors are located on a separate substrate than the control signal circuitry is located on, and connected to the control signal side using wire bonds.
Unfortunately, the galvanic isolation provided using these discrete high voltage capacitors is often insufficient for today's electronics equipment. For instance, because it is difficult to manufacture these discrete high voltage capacitors having matched capacitance values (e.g., within less than about 2 percent), the capacitors have inadequate transient immunity values. The discrete high voltage capacitors fail in other areas also.
Accordingly, what is needed in the art is a high voltage capacitor, and a method of manufacture therefore, that does not experience the drawbacks of the prior art discrete high voltage capacitors.